President Barack Obama urged Americans to help him end the country's "epidemic
of violence" by demanding the passage of his plan for the most drastic
overhaul of US gun laws in decades.

Flanked by schoolchildren at the White House, one month after the massacre of 20 young pupils at a primary school in Connecticut, Mr Obama told political opponents: "We can't put this off any longer".

"This time must be different," he said. "This time we must do something to protect our communities and our kids." Declaring the protection of America's children to be "our first obligation as a society," Mr Obama added: "This is how we will be judged".

Barack Obama launches sweeping $500 million gun violence plan (AP)

The president called for a ban on the sale of "military-style assault weapons" such as the rifle used at Sandy Hook elementary on December 14, noting that former President Ronald Reagan, the hero of today's Republican Party, urged Washington to prohibit their manufacture in 1994.

After several high-profile massacres involving 30-round ammunition cartridges, Mr Obama also proposed a ten-bullet limit. He also called for comprehensive criminal background checks on Americanstrying to buy firearms, and for new gun-trafficking laws to reduce the spread of weapons across the US.

As his plans were swiftly denounced by a string of high-profile Republicans and the pro-gun lobby, Mr Obama warned supporters: "The only way we can change is if American people demand it".

He cited a letter sent to him after the Sandy Hook shootings by a schoolgirl, who said: "I know that laws have to be passed by Congress. But I beg you to try very hard". Promising "I will try very hard", Mr Obama warned that the "American people need to make sure" their congressmen approved the plans.

The Republican-controlled House of Representatives is widely expected to oppose many of the measures. Yet Mr Obama's senior colleagues in the Senate, which is controlled by his Democratic party, have also warned that they will struggle to deliver his proposals through the upper chamber.

Marco Rubio, a Republican senator for Florida and potential presidential candidate, immediately vowed to "oppose the president's attempts to undermine Americans' constitutional right to bear arms." Mr Obama said in his remarks that this right must be weighed against Americans' rights to life and safety.

Tim Huelskamp, a senior Republican congressman for Kansas, said: "Taking away the rights and abilities of law-abiding citizens to defend themselves is yet another display of the Obama Administration's consolidation of power." Mr Obama also boasted, however, that he was using "the weight of this office" to immediately sign 23 separate executive orders. He commissioned research by government scientists into the potential effects of violent computer games, improvements to education and mental health services, and other tightening of existing gun control laws.

He also called on Republicans in Congress to end their six-year block on the appointment of a director to the bureau of Alcohol, Tobacco and Firearms, to help it carry out its work regulating weapons.

The plans were based on recommendations drawn up by Joe Biden, Mr Obama's vice-president, who led a task force on gun control action after the massacre at Sandy Hook.

Mr Biden said that he had "never seen the nation's conscience so shaken" as it had been by the incident. "We have a moral obligation to do everything in our power to diminish the prospect that something like this could happen again," he said.

The challenge facing Mr Obama was demonstrated vividly on the eve of his announcement when the National Rifle Association (NRA) released a provocative television advertisement The clip, which accused Mr Obama of being an "elitist hypocrite" for trying to restrict public access to guns while protecting his children with armed officers, was sharply criticised by the White House.

"Are the president's kids more important than yours?", the 35-second advertisement's narrator asked, in a deep, film-trailer-style voice. "Then why is he sceptical about putting armed guards in our schools when his kids are protected by armed guards at their school?"

Jay Carney, Mr Obama's press secretary, said: "To go so far as to make the safety of the president's children the subject of an attack ad is repugnant and cowardly".

The advertisement was condemned as "beyond the pale" by David Frum, a former speech writer for President George W. Bush, who noted that the Obamas had received several security threats. Robert Gibbs, a former senior adviser to Mr Obama, described it as "disgusting on many levels".

The NRA immediately condemned Mr Obama’s plans, saying “attacking firearms and ignoring children is not a solution”.

“Only honest, law-abiding gun owners will be affected and our children will remain vulnerable to the inevitability of more tragedy,” a spokesman said.

Aides to Mr Obama promised that he would mobilise the formidable campaign machinery that won him re-election last November in order to challenge the NRA's campaign against new regulations, which it has called "Stand and Fight".

"The president has the most exciting campaign apparatus ever built. It's time to turn that loose," Mr Gibbs told MSNBC. "If the NRA has a list [of names], then Obama for America has a bigger list."